Helen Ogg is an orphan at a Tennessee children's group home. After her adoption, she is visited by her biological father from another world. But there is a killer from her world who wants to make this world his own, a killer who knows of Helen and wants her dead. For in Helen's world the females are more powerful (having an evolutionary power, a power to freeze someone to death). They are instructed by her father to go to Mammoth Cave. There, the killer is waiting, and the adventure begins.